The Challenges of Virtual Hairstyling

May 28, 2010

The Challenges of Virtual Hairstyling

New system uses haptics to allow designers to comb hair just like they would in real life.

Imagine
that you had to design a virtual hairstyle by painstakingly defining the
position and shape of every single hair on a character’s head. It sounds like a
joke, but modeling hair in this way - with a heaping helping of
post-processing for added realism - remains the industry standard for creating virtual 3D hairstyles.

If
you were an animator at Pixar or Dreamworks, for your own sanity you might
avoid hair all together - say, by putting your characters in hats. How else to explain the
higher-than-expected frequency of baldness among recognizable computer-animated heroes?

Work from Ugo Bonanni and colleagues at MIRALab
at the University of Geneva promises to redress the sorry state of virtual
hairstyling in the most intuitive and natural way possible: by using
touch-sensitive, force-feedback technology - a.k.a. haptics
- to allow animators and even real-life hairstylists to style the coifs of
virtual characters in the same way they would style the hair of a real person.

This
isn’t the first time researchers have tried to simulate cutting, wetting,
drying and even moussing hair - that distinction belongs to Kelly Ward and
colleagues, whose 2007 Interactive Virtual Hair Salon managed to
transform the helmet-head that had previously afflicted one virtual character
into a more-realistic (but not necessarily improved) frizzy mop of overbleached
split ends appropriate for whichever mid-80’s music video they planned to drop her into. However,
Ward’s Virtual Hair Salon didn’t offer either combing or brushing - less
of an issue than you would think, given that the simulation also didn’t offer
virtual bed-head or, given enough computer cycles, gigantic
fused dreadlocks.

Bonanni’s
solution is to create virtual hair that can not only responds to virtual
combing in real time - it also delivers appropriate force-feedback to the
virtual hairbrush used to style it. This is, as Bonanni points out, a
non-trivial computing challenge:

“Displaying
a physically based simulation of a hairstyle with real-time animated hair
strands in contact with a styling tool returning haptic interaction forces is a
very ambitious endeavor which calls for a highly efficient and accurately
synchronized multithreaded application. […]

Fundamental
requirements to the visuo-haptic hair simulation models underlying a 3D styling
application include the ability to define the precise placement of hair
strands, the handling of both interaction forces and torques, and an
appropriate force/torque accumulation and propagation mechanism synchronizing
the visual and haptic modalities in a consistent way.”

Indeed,
one could argue this particular application is one of the more important uses
of the incredible power of today’s so-called “desktop
supercomputers,” which, let’s face it, are for the most part sitting idle,
their designers constantly on the hunt for a task big enough to warrant their brand
of awesome.

This
interface is the result:

By adding in the use of the keyboard, users can expand the power of their virtual hairbrush - which, unlike a regular hairbrush, is not bound by conventional notions of time, space or, given the look sported by the researcher’s test model, beauty:

And,
while we’re at it, here is the equation for a single strand of hair:

In
their conclusion, the researchers look forward to a revolution in virtual
hairstyling enabled by the unstoppable march of Moore’s Law:

“Application
of the proposed interaction metaphors to a complete hairstyling interface
relying on a simulation model enabling the explicit positioning of arbitrary
centerline nodes […] together with appropriate parallelization schemes
exploiting multicore architectures, could lead to a more robust implementation
of haptics-based hairstyling applications and a breakthrough in 3D hair
modeling.”